Search

Abstract: We investigated the optimum structure for Ti-containing Hf-based high-k gate dielectrics to achieve EOT scaling below 1nm. TiO2/HfSiO/SiO2 trilayer and HfTiSiO/SiO2 bilayer structures were fabricated by a newly developed in-situ PVD-based method. We found that thermal diffusion of Ti atoms to SiO2 underlayers degrades the EOT–J g characteristics. Our results clearly demonstrated the impact of the trilayered structure with TiO2 capping for improving EOT–J g characteristics of the gate stack. We achieved an EOT scaling of 0.78nm as well as reduced gate leakage of 7.2×10−2 A/cm2 for a TiO2/HfSiO/SiO2 trilayered high-k dielectric while maintaining the electrical properties at the bottom interface. [Copyright &y& Elsevier]

The theoretical temporal resolution limit t T of a silicon photodiode (Si PD) is 11.1 ps. We call "super temporal resolution" the temporal resolution that is shorter than that limit. To achieve this resolution, Germanium is selected as a candidate material for the photodiode (Ge PD) for visible light since the absorption coefficient of Ge for the wavelength is several tens of times higher than that of Si, allowing a very thin PD. On the other hand, the saturation drift velocity of electrons in Ge is about 2/3 of that in Si. The ratio suggests an ultra-short propagation time of electrons in the Ge PD. However, the diffusion coefficient of electrons in Ge is four times higher than that of Si. Therefore, Monte Carlo simulations were applied to analyze the temporal resolution of the Ge PD. The estimated theoretical temporal resolution limit is 0.26 ps, while the practical limit is 1.41 ps. To achieve a super temporal resolution better than 11.1 ps, the driver circuit must operate at least 100 GHz. It is thus proposed to develop, at first, a short-wavelength infrared (SWIR) ultra-high-speed image sensor with a thicker and wider Ge PD, and then gradually decrease the size along with the progress of the driver circuits. [ABSTRACT FROM AUTHOR]

Abstract: We fabricated novel poly-Si/TiN/HfSiO/SiO2 gate stacks by using an in-situ oxygen treatment process of a TiN electrode surface in order to suppress Si diffusion from poly-Si upper layer during post deposition annealing (PDA). The Si depth profile after PDA showed that no Si diffused into oxidized stacks due to the formation of TiON layers as a Si diffusion barrier. Furthermore, a high effective work function (EWF) of 4.94 eV was obtained from the oxidized stack even after PDA at 1000 °C. This high EWF is due not only to Si diffusion barrier formation but also to oxygen vacancy compensation by diffused-oxygen from the TiON layer. However, we observed significant growth of interfacial SiO2 after high temperature annealing. These results indicate a trade-off relationship between EWF control and equivalent oxide thickness (EOT) scaling, and imply that an additional method for EWF modulation is required for scaled high-k devices. [Copyright &y& Elsevier]

Abstract: Germanium (Ge)-based high-mobility metal-oxide-semiconductor field-effect transistors (MOSFETs) have gained considerable attention because they perform better than common Si-based devices. Although degraded electrical property of germanium oxide (GeO2) gate insulators is considered the most serious obstacle for implementing Ge-channel for future MOSFETs, remarkable progress has been made recently. This article overviews both fundamental and technological aspects of thermally grown GeO2, and discusses strategies for achieving ultrathin gate insulators for high-performance Ge-based MOSFETs. Our experimental and theoretical studies revealed that, despite excellent electrical property of GeO2/Ge interface, its poor stability is a big concern, especially for ultrathin dielectrics. To overcome this problem, we investigated the impact of plasma nitridation of Ge and GeO2 surfaces, in terms of surface cleaning, stability, and electrical properties of the nitrides. On the basis of the experimental findings, we have proposed high-quality Ge oxynitride (GeON) gate dielectrics, which consist of stable nitrogen-rich capping layers on ultrathin oxides. We implemented the GeON gate dielectrics into Ge-channel pMOSFETs and successfully demonstrated hole mobility that was 2.4 times higher than Si universal mobility. [Copyright &y& Elsevier]

We show how to improve microfocus X-ray radiography by using the SOPHIAS silicon-on-insulator pixel detector in conjunction with an amplitude grating. Single-exposure multi-energy absorption and differential phase contrast imaging was performed using the single amplitude grating method. The sensitivity in differential phase contrast imaging in a two-pixel-pitch setup was enhanced by 39% in comparison with the previously reported method [Rev. Sci. Instrum. 81, 113702 (2010).] by analyzing charge-sharing effects. Small-angle-scattering imaging was also possible in the two-pixel-pitch setup by counting the number of X-ray photons passing the pixel boundaries.

In this study, we examined five types of phase gratings in a two-dimensional (2D) single grating interferometer with multidot metal targets embedded in a diamond substrate. For a phase grating consisting of two stacked 1D π/2-phase gratings and a checkerboard π-phase grating the multidot-pattern self-images with high visibility (40%) were obtained as expected from simulations. In addition to an absorption image, differential phase contrast and dark-field images in both x and y directions were derived from a single image. We also examined face-centered-square multidot metal targets, which doubled the x-ray intensity, and obtained differential phase contrast images in both x and y directions.

Using multidot metal targets embedded in a diamond substrate, we created a single-grating Talbot-Lau interferometer and used it to capture two dimensional (2D) x-ray phase images. The ensemble of these targets constitutes a tiny virtual array of x-ray source and enables x-ray phase-contrast imaging with no source or absorption grating within a 1 m source-detector distance for 8 keV x-rays. We directly resolved a dot-pattern self-image of the phase grating with 6 µm pitch by using an x-ray image detector with 24 µm pixels and obtained 2D differential-phase and dark-field images from a single-exposure. Using the 2D differential-phase images, we also obtained a phase image with no streak artifacts.

We performed x-ray phase contrast imaging (XPCI) by Talbot-Lau interferometer using only a single transmission grating. Multiline metal targets embedded in a diamond substrate were irradiated with electrons to generate an array of x-ray lines of 1 μm width, which allowed XPCI within a 1 m source-detector distance in a configuration without a source or absorption grating. We directly resolved the self-image of the phase grating of 3 μm pitch using an x-ray image detector of 24 μm pixel size and successfully obtained absorption, differential phase, and dark-field images for 8 keV x rays.

We demonstrate hard x-ray phase contrast imaging (XPCI) using a tabletop Talbot-Lau interferometer in which the x-ray source and source grating are replaced with an x-ray source with multiline metal targets embedded in a diamond substrate. This source realizes an array of linear x-ray sources of a few micrometers width without fabrication difficulty because of the shallow penetration depth of electrons irradiated to the metal targets. This enhances the coherence of x rays from each linear source and allows XPCI within 45 cm source-detector distance under 1.2 W input power for 8 keV x rays.